Navigating between screens in a Flutter app¶

If your Flutter app has several screens, you can add voice commands to navigate through the app. For example, if the app shows a list of products, you may let the user open product details and then go back to the products list with voice. In this tutorial, we will add a new screen to our simple Flutter app and create voice commands to navigate between the app screens.

Note

If you are a visual learner, watch this tutorial on Alan AI YouTube Channel.

What you will learn¶

How to send commands to a Flutter app
How to handle commands on the Flutter app side
How to navigate between screens of a Flutter app with voice

What you will need¶

To go through this tutorial, make sure the following prerequisites are met:

You have completed the following tutorial: Building a voice assistant for a Flutter app.
You have set up the Flutter environment and it is functioning properly. For details, see Flutter documentation.
The device on which you are planning to test drive the Flutter app is connected to the Internet. The Internet connection is required to let the Flutter app communicate with the voice script run in the Alan Cloud.

Step 1: Add a new screen to the Flutter app¶

Note

This step is required if you are using the Flutter app created in the previous tutorial. You can also use your own app with several screens. In this case, skip this step and go to step 2.

In the Building a voice assitant for a Flutter app tutorial, we have created a single-screen Flutter app with the Alan button. Now let’s add a new screen to this app.

Open the app, go to the main.dart file and add the code for the second screen:

/// Add the second screen
class SecondPage extends StatefulWidget {
  const SecondPage({Key? key}) : super(key: key);

  @override
  _SecondPageState createState() => _SecondPageState();
}

class _SecondPageState extends State<SecondPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Flutter Demo Second Page"),
      ),
      body: Center(
        child: ElevatedButton(
            child: Text("Go back"),
            onPressed: () {
              Navigator.pop(context);
            }
        ),
      ),
    );
  }
}

In the MaterialApp constructor, define the app routes:

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
      /// Define the app routes
      initialRoute: '/',
      routes: {
        '/second': (context) => const SecondPage(),
      }
    );
  }
}

The second screen contains only one button that brings us back to the home screen. Let’s also add a button to the home screen to navigate to the second screen. To the body of the home screen, add the following button code:

...
@override
  Widget build(BuildContext context) {
    return Scaffold(
      ...
      body: Center(
        child: Column(
          ...
          children: <Widget>[
            ...
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            /// Add a button
            ElevatedButton(
              child: Text("Open the second screen"),
              onPressed: () {
                Navigator.pushNamed(context, '/second');
              }
            ),
          ],
        ),
      ),
      ...
    );
  }
...

You can test it: run the app. Now our app has two screens, and we can navigate between them. Tap the Open the second screen and Go back buttons to go to the second screen and back.

Step 2: Add voice commands for navigation¶

We need to add new commands to the Alan script to navigate between screens with voice. In Alan Studio, open the project and in the code editor, add the following intents:

intent('Open the second screen', p => {
        p.play({command: 'forward'});
        p.play('Opening the second screen');
});

intent('Go back', p => {
        p.play({command: 'back'});
        p.play('Going back');
});

Now, when we say one of these commands to the app, two things happen:

Alan sends the command provided in the intent to the Flutter app. To send the command, we need to specify a JSON object in the p.play function. In this tutorial, the object contains the command name and the route we want to pass to the app: forward or back.
Alan plays back the action confirmation to us.

Step 3: Handle commands on the app side¶

When we say Open the second screen or Go back, Alan sends a command to the Flutter app. We need to handle this command on the app side and make sure an appropriate action is performed. To do this, we will add a handler in the app.

In the main.dart file, update the onCommand handler:

class _MyHomePageState extends State<MyHomePage> {
    ...
    _MyHomePageState() {
      AlanVoice.addButton(
        "976d23299e2cfbc77d43485dbc3cb44a2e956eca572e1d8b807a3e2338fdd0dc/stage",
        buttonAlign: AlanVoice.BUTTON_ALIGN_LEFT);

      /// Update the onCommand handler
      AlanVoice.onCommand.add((command) => _handleCommand(command.data));
    }
...
}

To the _MyHomePageState class, add the _handleCommand() function to handle commands passed from the voice script:

...
    void _handleCommand(Map<String, dynamic> command) {
      switch(command["command"]) {
        case "forward":
          Navigator.pushNamed(context, '/second');
          break;
        case "back":
          Navigator.pop(context);
          break;
        default:
          debugPrint("Unknown command");
      }
    }
...

Here is how it works: when the Flutter app receives some command from the voice script, _handleCommand is invoked. If the sent command is forward, the second screen is open. If the sent command is back, we are brought to the home screen in the app.

You can test it: run the app on the device, tap the Alan button and say: Open the second screen. Then say Go back.

What’s next?¶

Have a look at the next tutorial: Passing the app state to the voice script.